It is well known that koalas have extremely specialised feeding habits. Koalas are natives of Australia and are one of the few mammals whose diet consists almost exclusively of the leaves of native eucalypt trees. Eucalyptus trees contain eucalypt oils which are toxic to most animal species. Koalas have a metabolism which is adapted to cope with these toxins.
However, koalas from a given area feed almost exclusively on a diet made up of only a very limited number of Eucalyptus species. This specialised feeding behaviour makes it very difficult to successfully keep koalas in zoos, particularly where the required Eucalyptus species are not freely available. In practice, it is necessary to give the animals fresh leaves each day.